Tropical Medicine and Infectious Diseases

Human Ehrlichiosis

Ehrlichiosis caused by gram negative, obligately intracellular bacteria belonging to the genus Ehrlichia of the family Anaplasmataceae, Order Rickettsiales and the alpha sub-division Proteobacteria. Though they have a characteristic Gram negative cell wall structure, they lack the important enzymes to synthesize cell membrane components likewise lipopolysaccharide and peptidoglycan. As intracellular pathogens, Ehrlichia reside in cytoplasmic membrane-bound vacuoles inside host cells by forming microcolonies called morulae, which is derived from the Latin word “morus” for mulberry. Morulae range 1.0 to 6.0 µm in diameter which may contain uniform or mixed cell types.